Open AccessMicrostructural and Chemical Investigations of Presolar Silicates from Diverse Stellar Environments
Author(s) -
Manish N. Sanghani,
Luc Lajaunie,
K. K. Marhas,
William D.A. Rickard,
Shih-Hsin Hsiao,
Z. Peeters,
Hsien Shang,
Der-Chuen Lee,
José J. Calvino,
Martin Bizzarro
Publication year - 2022
Publication title -
astrophysical journal/the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.3847/1538-4357/ac3332
Subject(s) - forsterite , enstatite , presolar grains , silicate , olivine , chondrite , pyroxene , astrochemistry , physics , meteorite , carbonaceous chondrite , chemical composition , astrophysics , geology , astrobiology , interstellar medium , geochemistry , astronomy , galaxy , thermodynamics
We report the structural and chemical investigation of nine presolar silicate grains from the CH3/CB b 3 chondrite Isheyevo and CR2 chondrite Northwest Africa (NWA) 801. Five of these grains belong to group 1, likely condensed in low- to intermediate-mass asymptotic giant branch (AGB) stars, super-AGB stars, or core-collapse supernovae, while the remaining four grains belong to group 4 and have a supernova origin. The advanced transmission electron microscopy and associated electron spectroscopy analyses show a diverse range of chemical and structural compositions for presolar silicates. Two GEMS (glass with embedded metal and sulfide)-like silicates, each from different groups, condensed under nonequilibrium conditions in stellar outflows. Two nonstoichiometric silicates from group 1 have dissimilar formation and alteration histories. An amorphous silicate from group 1 with olivine-like [(Mg,Fe) 2 SiO 4 ] composition likely formed as a crystalline olivine that subsequently amorphized in the interstellar medium. An oldhamite (CaS) grain within a stoichiometric enstatite (MgSiO 3 ) from group 1 probably formed by heterogeneous condensation in circumstellar outflows. Of the two crystalline grains from group 4, one is an antigorite [(Mg,Fe) 3 Si 2 O 5 (OH) 4 ], while the other is a nontronite [Na,Fe 2 (Si,Al) 4 O 10 (OH) 2 .nH 2 O], both formed as a crystalline forsterite and later altered to have hydrated silicate composition. A group-4 silicate has a chemical composition similar to a low Ca-pyroxene [(Ca,Mg)(Si,Al) 2 O 6 ]. Our data imply that presolar grains from different groups can have a similar range of grain-formation conditions.